I do not have a concrete idea. But I can think of something, e.g.
(1) image upload functionality
(2) display functionality with thumb-nail/bounding box constraint
Based on these situations, I can use these kind of scripts (e.g. lightbox, highslide etc.).

This time, I left (1), and made a method in the markdown interpretation which blog demo already has.
[Updated: Feb 22, 2009]
Collection of the enhancements:http://code.google.c...gdemo-enhanced/